These are not really very loud at all on my car, even my wife likes them. I have them connected straight to reducers on my Tri-Y headers with no cross over pipe.
I have the factory style sound absorbing material under the carpet, but even outside the car these are not really that loud, to be honest I was expecting them to be a bit obnoxious. My car is a base C code 289 so if you are running a higher compression engine they may be a bit louder.
For the price and simple nature of these pipes you cant go wrong!